When you're about to gain your third source point slot, if you have pet pal, return to the lady vengeance immediately and re-spec it to something else.

I had not saved for a little while so I was blind-sided by this and was unwilling to lose an hour of progress. When I unlocked the third source point, pet pal was removed from my collection of talents and I was not refuned a talent point.

Talent points are the most valuable resource in a character build, so I find this pretty upsetting.

I don't know if this event changes based upon what order you do things in, so I'm putting some specifics in spoiler tags:
The specific thing that happened was after I helped Hannag. She was the second to help me unlock a source point, but it may be that her "unlock method" is the specific one that removes pet pal.